Master information carrier and method for manufacturing magnetic disc using the same

ABSTRACT

A master information carrier capable of manufacturing a magnetic recording medium in which a preformat recording of information signals causing no reproduction signal detection errors arising from a pulse shift of a reproduction waveform is performed. A master information carrier  1  has an array of ferromagnetic thin films  3  arranged according to the pattern of information signals and is used for forming magnetization  4  of a pattern corresponding to the array pattern of the ferromagnetic thin film  3  in a magnetic recording medium by applying a magnetic field while opposing the master information carrier  1  against a magnetic recording medium  2.  Each of the ferromagnetic thin films  3  is formed such that each pattern length A becomes equal to a length including a correction amount a in addition to a length a between magnetic transition areas  6  of the magnetization  4  to be formed in the magnetic recording medium  2.

TECHNICAL FIELD

[0001] The present invention relates to a master information carrierused for performing a preformat recording of specific information for amagnetic disc and a method for manufacturing a magnetic disc using thesame.

BACKGROUND ART

[0002] At present, magnetic recording reproduction devices are beingdesigned to have higher recording density in order to achieve a largecapacity with a small size. In the field of a hard disc drive, which isa typical magnetic storage device, a device having an areal recordingdensity of more than 10 Gbits/in² is commercialized already, and such arapid progress in the technology can be observed that even the practicaluse of a device with 20 Gbits/in² is discussed.

[0003] As the technical background for enabling such high recordingdensity, significant factors are the improvement in the performance of amedium and in the performance of a head-disc interface as well as theimprovement in the linear recording density achieved by the appearanceof a new signal processing mode such as a partial response. Here, thepartial response is a mode of intentionally providing a knownintersymbol interference at the time of waveform equalization conductedfor avoiding an intersymbol interference when the linear recordingdensity is increased. This mode is characterized in that thedeterioration of a bit error rate can be prevented compared to aconventional peak detection or an integral detection.

[0004] In recent years, however, in addition to the appearance of such asignal processing mode, the main factor for improving the surfacerecording density is that the tendency toward an increase in the trackdensity is significantly exceeding the tendency toward an increase inthe linear recording density. This is due to the fact that amagneto-resistive type head, which has exceedingly excellentreproduction output performance compared to a conventional inductivetype magnetic head, has come into practical use. At present, due to thecommercialization of the magneto-resistive type head, a signal with atrack width as small as several IL m can be reproduced at an excellentS/N ratio. On the other hand, along with a further improvement in theperformance of the head in the years to come, a track pitch is expectedto reach the submicron range in the near future.

[0005] Now, for a magnetic head to scan such narrow tracks accuratelyand to reproduce signals at an excellent S/N ratio, the tracking servotechnology of the head plays an important role. As for such trackingservo technology of present hard disc drives, recording tracks areformed in circular manner on a hard disc. And within a revolution of thedisc, that is, within an angle of 360 degrees, a single region called awedge is repeatedly provided at a constant interval, where a servosignal for tracking, an address information signal and a reproductionclock signal etc. are recorded. Hereinafter, the servo signal fortracking, the address information signal and the reproduction clocksignal etc. are referred to as preformat signals, and the process ofrecording these signals in advance is referred to as a preformatrecording. The magnetic head reproduces these signals at a constantinterval so as to scan on the tracks accurately while identifying andcorrecting the position of the head.

[0006] The above-mentioned preformat signals such as the servo signalfor tracking, the address information signal and the reproduction clocksignal serve as reference signals for the magnetic head to scanaccurately on the tracks. Therefore, when these signals are recorded,positioning is required to be performed correctly with precision. In apresent hard disc drive, after a disc is incorporated into the drive, byusing a single-purpose servo recording device called a servo trackwriter, a preformat recording is performed by strictly controlling theposition of a magnetic head.

[0007] The preformat recording of the signals such as the servo signalfor tracking, the address information signal and the reproduction clocksignal by the magnetic head with the use of the single-purpose servotrack writer as mentioned above has the following problems.

[0008] First, a recording by a magnetic head basically is a linearrecording based on the relative movement of a head and a medium.Therefore, the above-mentioned method for recording by strictlycontrolling the position of the magnetic head with the single-purposeservo track writer requires a great amount of time for the preformatrecording. In addition, since the single-purpose servo track writer isquite expensive, the cost for the preformat recording becomes extremelyhigh.

[0009] Secondly, due to a spacing between the head and the medium, anddue to a broadening of a recording magnetic field caused by the poleshape of the recording head, the magnetic transition lacks in sharpnessin the track edge portion of the recorded preformat signals. In thepresent tracking servo technology, the position of a head is detected bythe change in the reproduction output amplitude at the time when thehead went off-track and scanned. Therefore, with regard to the signaltracks where the preformat recording was performed, the reproducedsignal is not only required to have an excellent S/N ratio when scanningaccurately on the tracks just as when data signals recorded betweenservo areas are reproduced, but also to have a steep change in thereproduction output amplitude at the time when the head went off-trackand scanned, that is, sharp off-track characteristics. The above problemgoes against this requirement, which makes it difficult to provide theaccurate tracking servo technology for recording of submicron tracks inthe years to come.

[0010] Now, as means to solve the problems in the preformat recording bythe magnetic head as mentioned above, the preformat recording technologyproposed by the present inventors in JP10(1998)-40544A mainly is thetechnology of using a master information carrier including a base onwhich a pattern of ferromagnetic thin films corresponding to informationsignals is formed, and bringing the surface of the master informationcarrier into contact with the surface of a magnetic recording medium soas to perform a surface transcription recording as a whole of amagnetization reversal pattern corresponding to the pattern of theferromagnetic thin films formed on the surface of the master informationcarrier for a magnetic recording medium.

[0011] According to the configuration disclosed by the same publication,the magnetization reversal pattern corresponding to the pattern of theferromagnetic thin films in the master information carrier istranscribed and recorded in the lump on the magnetic recording medium bya recording magnetic field arising from the ferromagnetic thin filmsformed on the surface of the master information carrier, which ismagnetized in one direction. In other words, by forming patterns of theferromagnetic thin films corresponding to the servo signal for tracking,the address information signal and the reproduction clock signal etc. onthe surface of the master information carrier by the photolithographictechnique etc., the information signals corresponding thereto can berecorded in the magnetic recording medium for the preformat recording.

[0012] While a recording by a conventional magnetic head basically is adynamic linear recording based on the relative movement of a head and amedium, the above-mentioned configuration is characterized in that thisrecording is a static areal recording without accompanying relativemovement of the master information carrier and the medium. Due to such afeature, the technology disclosed in JP10(1998)-40544A can be extremelyeffective for solving the above-mentioned problems related to thepreformat recording, as will be explained below.

[0013] First, due to the feature of surface recording, the time requiredfor the preformat recording is much shorter than that for recording bythe conventional head. Moreover, the expensive servo track writer forrecording while strictly controlling the position of the magnetic headis not required. Therefore, the productivity related to the preformatrecording can be improved significantly, and at the same time, theproduction cost can be reduced.

[0014] Secondly, due to the feature of static recording withoutaccompanying relative movement of the master information carrier and themedium, a spacing between the surface of the master information carrierand the surface of the magnetic recording medium at the time ofrecording can be reduced to a minimum by securely contacting them toeach other. Moreover, the broadening of a recording magnetic field dueto the pole shape of the recording head does not occur as in the casewith the recording by a magnetic head. Therefore, the magnetictransition at the track edge portion where the preformat recording wasperformed has excellent sharpness compared with the recording by aconventional magnetic head, and more accurate tracking is possible.

[0015] One example of the surface configuration of a conventional masterinformation carrier disclosed in the same publication is shown in FIG.21. FIG. 21 shows a disc-shaped master information carrier configured soas to perform a lump sum recording of preformat signals for a magneticrecording medium such as a hard disc, and wedge pattern areas 74 areformed in one circle of a disc, that is, over an angle of 360 degrees ata constant interval, with pattern shapes of ferromagnetic thin filmscorresponding to preformat signals such as a servo signal for tracking,an address information signal and a reproduction clock. In addition, 75shows areas between wedges, and these areas correspond to data areas ona magnetic recording medium. Also, 76 is a marker used for positioningthe magnetic recording medium at the time when it is closely contactedwith the surface of the master information carrier.

[0016] An enlarged view of a portion A of the master information carriershown in FIG. 21 is shown in FIG. 22. FIG. 22 shows the patternconfiguration of ferromagnetic thin films 63 formed according to thepreformat signals inside the wedge, which is provided at a constantangle in the circumferential direction of the magnetic recording medium,only for 10 tracks in the radial direction of a master informationcarrier 62 (that is, in the direction of recording track width). Alsofor reference, in the area between wedges 75, track portions where datawill be recorded on the magnetic recording medium after the preformatsignals are recorded in the magnetic recording medium are shown bybroken lines. On the surface of an actual master information carrier,patterns of the ferromagnetic thin films as shown in FIG. 22 are formed,according to the recording area of the magnetic recording medium wherethe preformat signals are recorded, at a constant angle in thecircumferential direction and also for all the recording tracks in theradial direction of the disc.

[0017] The preformat signals are formed as arrays of the ferromagneticthin films 63 included, for example as shown in FIG. 22, in the areas ofthe clock signal, the servo signal for tracking, the address informationsignal etc., and each area is arranged sequentially in the longitudinaldirection of the track on the surface of the master information carrier62. The hatched portions in FIG. 22 are the ferromagnetic thin films 63.In addition, the planar shapes of the ferromagnetic thin films 63 inFIG. 22 are all rectangular, but in fact the shapes are not limitedthereto and can be formed into different shapes according to theembodiment.

[0018]FIG. 23 and FIG. 24 show examples of cross-sectionalconfigurations of the master information carrier of FIG. 22 taken onalternate long and short dash line LL′. The alternate long and shortdash line LL′ corresponds to the circumferential direction of themagnetic recording medium, and the lateral direction of the surface alsomatches the time base direction of the signal at the time when thesignal recorded in the magnetic recording medium is reproduced by amagnetic head. The magnetic information carrier 62 may be configuredsuch that pattern shapes made of the ferromagnetic thin films 63 areburied and arranged in a surface portion of a nonmagnetic base 64 asshown in FIG. 23, or such that pattern shapes made of the ferromagneticthin films 63 are arranged in the form of protrusions on the surface ofthe nonmagnetic base 64 as shown in FIG. 24. However, in view ofdurability or long-life of the master information carrier, theconfiguration shown in FIG. 23 is superior.

[0019] In the above-mentioned conventional preformat technology, thepatterns of the ferromagnetic thin films on the surface of the masterinformation carrier correspond to the magnetized pattern to be recordedin the magnetic recording medium. Therefore, the patterns of theferromagnetic thin films should be arranged, for example, in and on thesurfaces of the master information carriers illustrated in FIG. 23 andFIG. 24 such that a pattern length A of each ferromagnetic thin film ora distance B between the individual patterns of the ferromagnetic thinfilms corresponds to a desired signal length in a magnetized pattern tobe recorded in a magnetic recording medium, that is, to a length betweena pair of magnetic transition areas adjacent to each other in themagnetized pattern.

[0020] However, according to the examinations conducted by the presentinventors, the length between the magnetic transition areas in themagnetized pattern recorded on the magnetic recording medium in factdoes not accurately match the length A of each pattern of theferromagnetic thin films and the distance B between the individualpatterns of the ferromagnetic thin films. Therefore, when the patternlength A of the ferromagnetic thin films or the distance B between thepatterns of the ferromagnetic thin films is set so as to match thelength between the magnetic transition areas desired on the magneticrecording medium accurately, the length between the magnetic transitionareas actually recorded on the magnetic recording medium differs fromthe desired length. As a result, with regard to a reproduction waveformat the time when the recorded magnetized pattern is reproduced by amagnetic head, the position of the reproduction pulse is shifted fromthe desired pulse position by a certain time.

[0021] In this case, it would not be a problem when the shift quantityof the reproduction pulse mentioned above is sufficiently small in ratioto a detection window width of a reproduction signal processing circuit.However, when the amount exceeds the permissible limit of the detectionwindow width, the reproduction signal processing circuit cannot detectthe reproduction pulse, so that a reproduction signal error arises.

[0022] Furthermore, the preformat recording using the master discdisclosed in the same publication is effective not only for aconventional in-plane magnetic recording medium but also for a verticalmagnetic recording medium to be used for performing super high densityrecording in the future, and the development of its application isawaited.

[0023] The magnetic recording method for recording in a verticalmagnetic recording medium disclosed in the same publication will beexplained below. FIG. 25A to FIG. 25C are cross-sectional views of avertical magnetic recording medium 61 taken in the circumferentialdirection of a disc, and the lateral direction of the surface matchesthe time base direction at the time when a magnetized pattern to berecorded in the vertical magnetic recording medium 61 is reproduced by amagnetic head.

[0024] First, as shown in FIG. 25A, the vertical magnetic recordingmedium 61 where preformat signals are recorded is prepared. Next, asshown in FIG. 25B, the surface of the master information carrier 62 iscontacted closely with the surface of the vertical magnetic recordingmedium 61, and an external magnetic field 65 is applied in the directionperpendicular to the surface of this master information carrier 62. Inaddition, the example shown in FIG. 25B uses the master informationcarrier according to the configuration of FIG. 23, but the masterinformation carrier according to the configuration of FIG. 24 may beused as well.

[0025] By applying the magnetic field 65, leakage flux 66 correspondingto the shape pattern of the ferromagnetic thin films 63 is generated onthe surface of the master information carrier 62. Accordingly, recordedmagnetization 67 with a pattern corresponding to the shape pattern ofthe ferromagnetic thin films 63 is formed in the vertical magneticrecording medium 61 as shown in FIG. 25C.

[0026] As a result, as shown in FIG. 25C, in the vertical magneticrecording medium 61, a magnetized pattern, which includes a non-recordedarea corresponding to a portion between the ferromagnetic thin films onthe surface of the master information carrier and an area wheremagnetization was recorded by the leakage flux from theferromagnetic-thin films, is formed in which the two areas are arrangedalternately via a magnetic transition area 68. In addition, the recordedmagnetized pattern of FIG. 25C shows a case in which the verticalmagnetic recording medium 61 is erased to a neutral point in advance byapplying a magnetic field alternately in opposite directions or throughapplication of a thermomagnetization method or the like prior to therecording by using the master information carrier 62.

[0027] On the other hand, as shown in FIG. 26A, prior to the operationof closely contacting the vertical magnetic recording medium 61 with thesurface of the master information carrier 62, by applying a d.c.magnetic field to the vertical magnetic recording medium 61 andproviding initial magnetization 69, as shown in FIG. 26C, it is possibleto form the recorded magnetization 67 with a pattern including theresidual magnetization of the initial magnetization 69 and themagnetization recorded by the leakage flux 66, arranged alternately viathe magnetic transition area 68. In this case, the polarity of theinitial magnetization 69 should be opposite to the polarity of theapplied magnetic field 65. When the magnetized pattern recorded in thevertical magnetic recording medium 61 is reproduced by using a magnetichead, about twice as large a reproduction signal amplitude can beobtained from the recorded magnetized pattern shown in FIG. 26C as thatfrom the recorded magnetized pattern shown in FIG. 25C, so that thisconfiguration is more preferable.

[0028] In this way, as shown in FIG. 25B and FIG. 26B, when a preformatrecording is performed for a vertical magnetic recording medium, byapplying the magnetic field 65 in the direction perpendicular to thesurface of the master information carrier 62, the ferromagnetic thinfilms 63 are magnetized in the vertical direction of the film surface,that is, in the thickness direction. However, it became clear thatsufficient vertical recording performance cannot necessarily be obtainedby such a method.

[0029] This principle will be explained by referring to FIG. 27. 80shows a vertical magnetic field distribution in the vicinity of themaster information carrier surface obtained by the leakage flux 66 fromthe applied magnetic field 65 and the ferromagnetic thin films 63. Inorder to obtain excellent recording performance by the magneticrecording method disclosed in the same publication, by focusing magneticflux on the ferromagnetic thin film portions having high magneticpermeability inside the master information carrier, the magnetic fieldat the portion between the individual ferromagnetic thin films needs tobe reduced sufficiently compared to the volume of the applied magneticfield (the level shown by a straight line 81) and the magnetic field atthe ferromagnetic thin film surface needs to be increased sufficientlycompared to the volume of the applied magnetic field (the level shown bythe straight line 81).

[0030] However, as a result of further examinations conducted by thepresent inventors, it became clear that it is difficult to obtain thepreferable vertical magnetic field distribution as described above bythe method disclosed in the same publication. In other words, ademagnetizing field in the direction perpendicular to the film surfaceis strong inside the ferromagnetic thin films 63, so that sufficientlylarge leakage magnetic flux 66 contributing to the recording, that is, amagnetic field in the vertical direction, cannot be obtained at thesurface of the ferromagnetic thin films 63.

[0031] Furthermore, since the magnetic flux is not focused sufficientlyon the ferromagnetic thin films 63 inside the master informationcarrier, a strong vertical magnetic field exceeding the half of theapplied magnetic field 65 is generated also at the portion between theferromagnetic thin films 63. As a result, the recorded magnetization 67in the vertical magnetic recording medium 61 becomes much smaller thanthe value of the residual magnetization intrinsic in the verticalmagnetic recording medium 61, and the amplitude of a reproductionwaveform 82 reproduced from this recorded magnetized pattern (See FIG.27) becomes much smaller than a reproduction signal amplitude 83reproduced from the magnetized pattern recorded by a conventionalmagnetic head.

[0032] This problem can be solved to some degree by increasing thethickness of the ferromagnetic thin films 63 on the master informationcarrier 62 and reducing the demagnetizing field inside the ferromagneticthin films; However, in order to obtain sufficient improvement by theabove-mentioned method, it is necessary to increase the thicknessrelative to the pattern length of the ferromagnetic thin films shown inthe cross-sectional view of FIG. 27 at least as much as twice to threetimes. To form a shape pattern of ferromagnetic thin films having such ahigh aspect rate is extremely difficult from the viewpoint of thelithographic technique used in the manufacturing process of a masterinformation carrier.

[0033] In order to obtain a larger reproduction signal amplitude withthe conventional method disclosed in the same publication, as shown inFIG. 26A, it is necessary to erase the magnetization in the verticalmagnetic recording medium 61 by applying a d.c. magnetic field prior tothe operation of closely contacting the vertical magnetic recordingmedium 61 with the surface of the master information carrier 62, and toprovide the initial magnetization 69 for the vertical magnetic recordingmedium 61.

[0034] However, a vertical magnetic recording medium has a strongdemagnetizing field in the direction perpendicular to the film surfaceof a magnetic layer, so that it is difficult to realize the d.c. erasingstate uniformly and stably in a large area over the entire disc surface.That is, due to the demagnetizing field at the time when themagnetization is erased by applying a d.c. magnetic field, the initialmagnetization 69 in the vertical magnetic recording medium 61 becomesextremely small compared to the value of the residual magnetizationintrinsic in the vertical magnetic recording medium 61.

[0035] Furthermore, in the course of time after the application of ad.c. magnetic field, the magnetic domains in which the magnetization islocally reversed by the demagnetizing field increase, so that theinitial magnetization 69 is further demagnetized. Therefore, it isdifficult to obtain a uniform and sufficiently large reproduction signalamplitude over the entire disc surface by the conventional methoddescribed above.

[0036] In view of the foregoing problems, it is a first object of thepresent invention to solve the above-mentioned problems in the preformattechnology disclosed in JP10(1998)10-40544A and to provide a masterinformation carrier capable of recording preformat signals causing noreproduction signal errors in an in-plane magnetic recording medium byapproximating a length between magnetic transition areas of a magnetizedpattern to be recorded in an in-plane magnetic recording medium by apreformat recording to a more desirable set point, and also to providean in-plane magnetic recording medium capable of accurate servo trackingby using this master information carrier. Furthermore, a second objectis to provide a master information carrier capable of recordingpreformat signals in a vertical magnetic recording medium exhibiting auniform and sufficient large reproduction signal amplitude over theentire disc surface, and also to provide a vertical magnetic recordingmedium capable of accurate servo tracking by using this masterinformation carrier.

DISCLOSURE OF THE INVENTION

[0037] In order to achieve the first object mentioned above, a firstconfiguration of a master information carrier according to the presentinvention has an array of ferromagnetic films formed on a base surfaceaccording to information signals, the master information carrier beingused for forming a magnetized pattern corresponding to the array of theferromagnetic films in an in-plane magnetic recording medium throughapplication of a magnetic field with the master information carrieropposing the in-plane magnetic recording medium, wherein a length ofeach ferromagnetic film is larger than a length between magnetictransition areas of the magnetized pattern to be formed by theferromagnetic film in the in-plane magnetic recording medium.

[0038] Furthermore, to achieve the first object mentioned above, asecond configuration of a master information carrier according to thepresent invention has an array of ferromagnetic films formed on a basesurface according to information signals, the master information carrierbeing used for forming a magnetized pattern corresponding to the arrayof the ferromagnetic films in an in-plane magnetic recording mediumthrough application of a magnetic field with the master informationcarrier opposing the in-plane magnetic recording medium, wherein adistance between neighboring ferromagnetic films is smaller than alength between magnetic transition areas of the magnetized pattern to beformed by each ferromagnetic film in the in-plane magnetic recordingmedium.

[0039] When the magnetic field is applied to the master informationcarrier, the magnetic transition areas of the magnetized patterns formedby the leakage magnetic flux from each ferromagnetic film in thein-plane magnetic recording medium are located on the inner side ratherthan the both edge portions of the ferromagnetic films. Therefore,according to the first and second configurations mentioned above, thelength between the magnetic transition areas of the magnetized patternformed in the in-plane magnetic recording medium can be determined asdesired. Thus, a master information carrier capable of recordinginformation signals without a pulse shift in an in-plane magneticrecording medium can be provided.

[0040] Furthermore, to achieve the first object, a first method formanufacturing a magnetic recording medium according to the presentinvention includes the steps of overlapping the master informationcarrier according to the above-mentioned first or second configurationson an in-plane magnetic recording medium, applying a magnetic field andthus performing a preformat recording of the magnetized patterncorresponding to the array of the ferromagnetic films in the masterinformation carrier for the in-plane magnetic recording medium.Accordingly, an in-plane magnetic recording medium without reproductionsignal detection errors can be provided.

[0041] In order to achieve the second object mentioned above, a secondmethod for manufacturing an information recording medium according tothe present invention is a manufacturing method for a magnetic recordingmedium including the step of applying a magnetic field while opposing amaster information carrier provided with an array of ferromagnetic filmsformed according to information signals on a base surface against asurface of a vertical magnetic recording medium and thus performing apreformat recording of a magnetized pattern corresponding to the arrayof the ferromagnetic films for a magnetic layer in the vertical magneticrecording medium, wherein the magnetic field is applied parallel to thesurface direction of the ferromagnetic film and to the magnetic layer ofthe vertical magnetic recording medium.

[0042] According to this method, the demagnetizing field in therespective ferromagnetic films is small, and magnetic paths with smallmagnetic resistance are formed successively in the in-plane of themaster information carrier, so that leakage flux with a sufficientlylarge vertical directional component compared to the volume of theapplied magnetic field can be obtained. As a result, a large magneticfield amplitude with reversed polarities to each other can be obtainedin the vicinity of the both edges of the ferromagnetic film. Thus,without providing initial magnetization in advance, a vertical magneticrecording medium can be manufactured in which a preformat recording ofinformation signals with large reproduction signal amplitudes isperformed.

BRIEF DESCRIPTION OF THE DRAWINGS

[0043]FIG. 1 is an explanatory diagram schematically showing aconfiguration example of a master information carrier according to anembodiment of the present invention and the relationship with areproduction waveform obtained by reproducing preformat signals recordedwith the use of this master information carrier by a magnetic head.

[0044]FIG. 2 is an explanatory diagram schematically showing anotherconfiguration of a master information carrier according to an embodimentof the present invention and the relationship with a reproductionwaveform obtained by reproducing preformat signals recorded with the useof this master information carrier by a magnetic head.

[0045]FIG. 3 is an explanatory diagram schematically showing yet anotherconfiguration of a master information carrier according to a firstembodiment of the present invention and the relationship with areproduction waveform obtained by reproducing preformat signals recordedwith the use of this master information carrier by a magnetic head.

[0046]FIG. 4A to FIG. 4C are explanatory diagrams schematically showingone example of performing the step of preformat recording for anin-plane magnetic recording medium using the above-mentioned masterinformation carrier.

[0047]FIG. 5A to FIG. 5C are explanatory diagrams schematically showinganother example of performing the step of preformat recording for anin-plane magnetic recording medium using the above-mentioned masterinformation carrier.

[0048]FIG. 6 is an explanatory diagram schematically showing aconfiguration example of a conventional master information carrier andthe relationship with a reproduction waveform obtained by reproducingpreformat signals recorded with the use of this master informationcarrier by a magnetic head.

[0049]FIG. 7A to FIG. 7C are explanatory diagrams schematically showingone example of performing the step of preformat recording for a verticalmagnetic recording medium using a master information carrier accordingto a second embodiment of the present invention.

[0050]FIG. 8 is a cross-sectional view showing a configuration exampleof a master information carrier according to the second embodiment.

[0051]FIG. 9 is a cross-sectional view showing another configuration ofa master information carrier according to the second embodiment.

[0052]FIG. 10 is an explanatory diagram schematically showing a verticalmagnetic field distribution at the time of recording in a verticalmagnetic recording medium using a master information carrier accordingto the second embodiment and the relationship with a reproductionwaveform thereof.

[0053]FIG. 11A to FIG. 11C are explanatory diagrams schematicallyshowing another example of performing the step of preformat recordingfor a vertical magnetic recording medium using a master informationcarrier according to a second embodiment of the present invention.

[0054]FIG. 12 is a cross-sectional view showing the configuration of amagnetic recording device used for performing a preformat recording fora vertical magnetic recording medium using a master information carrieraccording to the second embodiment.

[0055]FIG. 13 is an explanatory diagram showing a configuration exampleof a magnetic transcription head installed in the above-mentionedmagnetic recording device.

[0056]FIG. 14 is an explanatory diagram showing another configuration ofa magnetic transcription head installed in the above-mentioned magneticrecording device

[0057]FIG. 15A is a plan view showing the configuration of a masterinformation carrier according to the second embodiment; FIG. 15B andFIG. 15C are explanatory diagrams schematically showing one example ofoperating a magnetic transcription head at the time of performing apreformat recording using this master information carrier.

[0058]FIG. 16A is a plan view showing the configuration of a masterinformation carrier according to the second embodiment; FIG. 16B andFIG. 16C are explanatory diagrams schematically showing another exampleof operating a magnetic transcription head at the time of performing apreformat recording using this master information carrier.

[0059]FIG. 17A is a plan view showing the configuration of a masterinformation carrier according to the second embodiment; FIG. 17B andFIG. 17C are explanatory diagrams schematically showing another exampleof operating a magnetic transcription head at the time of performing apreformat recording using this master information carrier.

[0060]FIG. 18A is a plan view showing the configuration of a masterinformation carrier according to the second embodiment; FIG. 18B andFIG. 18C are explanatory diagrams schematically showing yet anotherexample of operating a magnetic transcription head at the time ofperforming a preformat recording using this master information carrier.

[0061]FIG. 19A is a plan view showing the configuration of a masterinformation carrier according to the second embodiment; FIG. 19B andFIG. 19C are explanatory diagrams schematically showing yet anotherexample of operating a magnetic transcription head at the time ofperforming a preformat recording using this master information carrier.

[0062]FIG. 20A is a plan view showing the configuration of a masterinformation carrier according to the second embodiment; FIG. 20B andFIG. 20C are explanatory diagrams schematically showing yet anotherexample of operating a magnetic transcription head at the time ofperforming a preformat recording using this master information carrier.

[0063]FIG. 21 is a plan view showing the configuration of a conventionalmaster information carrier.

[0064]FIG. 22 is an enlarged plan view showing one portion of FIG. 21.

[0065]FIG. 23 is a cross-sectional view showing a configuration exampleof a conventional master information carrier.

[0066]FIG. 24 is a cross-sectional view showing another configuration ofa conventional master information carrier.

[0067]FIG. 25A to FIG. 25C are explanatory diagrams schematicallyshowing one example of performing the conventional step of preformatrecording for a vertical magnetic recording medium using a masterinformation carrier.

[0068]FIG. 26A to FIG. 26C are explanatory diagrams schematicallyshowing another example of performing the conventional step of preformatrecording for a vertical magnetic recording medium using a masterinformation carrier.

[0069]FIG. 27 is an explanatory diagram schematically showing a verticalmagnetic field distribution at the time of recording in a verticalmagnetic recording medium by using a conventional manufacturing methodand the relationship with a reproduction waveform thereof.

BEST MODE FOR CARRYING OUT THE INVENTION

[0070] In the following, embodiments of the present invention will beexplained in detail.

FIRST EMBODIMENT

[0071] First, the step of recording preformat signals, which isperformed as one of the steps for manufacturing an in-plane magneticrecording medium, will be explained briefly by referring to FIG. 4A toFIG. 4C. FIG. 4A to FIG. 4C are cross-sectional views taken in thecircumferential direction of a disc of an in-plane magnetic recordingmedium 2, and the lateral direction of the surface also matches the timebase direction at the time when a magnetized pattern to be recorded inthe in-plane magnetic recording medium 2 is reproduced with a magnetichead.

[0072] First, as shown in FIG. 4A, the in-plane magnetic recordingmedium 2 is prepared. In addition, the magnetization of the in-planemagnetic recording medium 2 shown in FIG. 4A is erased to a neutralpoint in advance by applying a magnetic field alternately in oppositedirections or through application of a thermomagnetization method or thelike.

[0073] Next, as shown in FIG. 4B, the side face of a master informationcarrier 1 where ferromagnetic thin films 3 are formed is contactedclosely with the surface of the in-plane magnetic recording medium 2,and a magnetic field 9 is applied. In addition, the example shown hereuses a master information carrier in which the ferromagnetic thin films3 are buried in the in-plane, but a master information carrier on whichthe ferromagnetic thin films 3 are formed as protrusions may be used aswell.

[0074] By applying the magnetic field 9, leakage flux 10 correspondingto a shape pattern of the ferromagnetic thin films 3 is generated on thesurface of the master information carrier 1. Accordingly, magnetization4 with a pattern corresponding to the shape pattern of the ferromagneticthin films 3 is formed in the in-plane magnetic recording medium 2 asshown in FIG. 4C.

[0075] As shown in FIG. 4C, the in-plane magnetic recording medium 2 nowhas a magnetized pattern including a non-recorded area, which is aportion facing the surface of the ferromagnetic thin films 3, and anarea where the magnetization 4 is recorded by the leakage flux 10, inwhich the two areas are arranged alternately via a magnetic transitionarea 6.

[0076] On the other hand, as shown in FIG. 5A, it is also possible toequally erase the in-plane magnetic recording medium 2 by applying ad.c. magnetic field in one direction and to provide initialmagnetization 11, and then, as shown in FIG. 5B, to contact the in-planemagnetic recording medium 2 closely with the surface of the masterinformation carrier 1 and to apply the magnetic field 9. Accordingly, asshown in FIG. 5C, a magnetized pattern can be recorded in which residualmagnetization 4a from the initial magnetization 11 and magnetization 4 brecorded by the leakage flux 10 are arranged alternately via themagnetic transition area 6. At this time, the polarity of the initialmagnetization 11 should be the opposite polarity to the polarity of theapplied magnetic field 9. When the magnetized pattern recorded in thein-plane magnetic recording medium 2 is reproduced by using a magnetichead, about twice as large a reproduction signal amplitude can beobtained by the method shown in FIG. 5A to FIG. 5C as that obtained bythe method shown in FIG. 4A to FIG. 4C.

[0077] Here, referring to FIG. 1, the relationship between the patternof the ferromagnetic thin films formed on the master information carrier1 of the present embodiment, the magnetized pattern to be recorded bythe preformat recording in the in-plane magnetic recording medium 2 bythis master information carrier 1 and a reproduction waveform of thismagnetized pattern reproduced by a magnetic head will be explained. Inaddition, in FIG. 1, the master information carrier 1 and the in-planemagnetic recording medium 2 are shown in cross-section taken in thecircumferential direction of the disc, and the lateral direction of thesurface matches the time base direction at the time when the magnetizedpattern to be recorded in the in-plane magnetic recording medium 2 isreproduced by using the magnetic head.

[0078] Now, for the purpose of comparing with FIG. 1, a conventionalmaster information carrier used in the preformat technology, amagnetized pattern recorded by a preformat recording in a conventionalin-plane magnetic recording medium by this master information and areproduction waveform of this magnetized pattern are shown in FIG. 6. Inaddition, the in-plane magnetic recording media 2 shown in FIG. 1 andFIG. 6 are provided in advance with the initial magnetization 11 andthen recorded by the preformat recording as already explained by usingFIG. 5A to FIG. 5C.

[0079] As shown in FIG. 6, according to the configuration in theconventional example, a pattern length A of the ferromagnetic thin filmsand a distance B between the patterns of the ferromagnetic thin films ina master information carrier 51 accurately match lengths betweenmagnetic transition areas a and b desired on an in-plane magneticrecording medium 52.

[0080] According to the examinations conducted by the present inventors,it became clear that in the in-plane magnetic recording medium 52 inwhich the preformat recording was performed by using the conventionalmaster information carrier 51, a magnetic transition area 56 in theactually recorded magnetized pattern is not located in an areacorresponding to both edges of ferromagnetic thin films 53 but islocated in an area that is slightly shifted inside from the both edgesof the ferromagnetic thin film 53, as shown in FIG. 6.

[0081] Thus, an actual length between the magnetic transition areas a,in the portion corresponding to the pattern length A of theferromagnetic thin films becomes shorter than the desired value a on thein-plane magnetic recording medium 52. On the contrary, an actual lengthbetween the magnetic transition areas b, in the portion corresponding tothe distance B between the patterns of the ferromagnetic thin filmsbecomes longer than the desired value b on the in-plane magneticrecording medium 52.

[0082] Accordingly, when the recorded magnetized pattern is reproducedby the magnetic head, there is a pulse shift arising between an actualreproduction waveform 55 and a desired reproduction waveform 57, whichcorresponds to the difference between a and a, or b and b, as shown inthe drawing. When this quantity of pulse shift exceeds the permissiblelimit of a detection window width of a reproduction signal processingcircuit, the reproduction signal processing circuit cannot detect thereproduced pulse, so that a reproduction signal error occurs.

[0083] On the contrary, as shown in FIG. 1, in the master informationcarrier 1 of the present invention, the shift quantity of the magnetictransition area 6 from the end portions of the ferromagnetic thin film 3is taken into account so as to obtain the desired lengths between themagnetic transition areas a and b in the magnetized pattern recorded onthe in-plane magnetic recording medium 2, and therefore, the patternlength A of the ferromagnetic thin films 3 and the distance B betweenthe patterns (See FIG. 23 and FIG. 24) are corrected in advance.

[0084] In other words, the pattern length A of the ferromagnetic thinfilms 3 is determined to be larger only by an appropriate correctionamount a than the desired length between the magnetic transition areas aon the in-plane magnetic recording medium 2, and the distance B betweenthe patterns of the ferromagnetic thin films 3 is determined to besmaller only by the correction amount α than the desired length betweenthe magnetic transition areas b on the in-plane magnetic recordingmedium 2. Accordingly, the desired lengths between the magnetictransition areas a and b can be obtained in the magnetized patternrecorded on the in-plane magnetic recording medium 2, and a desiredreproduction waveform 5 can be obtained.

[0085] In FIG. 1, the appropriate correction amount α can be estimated,for example, by observing the reproduction waveform in the conventionalexample shown in FIG. 6, from the difference between the desired lengthbetween the magnetic transition areas a and the actual length betweenthe magnetic transition areas a₁ or from the difference between thedesired length between the magnetic transition areas b and the actuallength between the magnetic transition areas b₁. The appropriatecorrection amount a differs depending on the magnetic property or thethickness of the ferromagnetic thin films 3 and the values of thedesired lengths between the magnetic transition areas a and b, andfurther on the magnetic property of the in-plane magnetic recordingmedium 2 and so forth, so that it is necessary to make an estimate foreach embodiment on the basis of experimental experiences as mentionedabove.

[0086] In one example, the experiment was conducted by using a Co filmwith saturation magnetic flux density of 1.6T as the ferromagnetic thinfilm 3 on the master information carrier 1 under the conditions wherethe thickness of the ferromagnetic thin film 3 was between 0.2 μm and1.0 μm, the desired lengths between the magnetic transition areas a, bwere between 0.5 μm and 5.0 μm, and the coercivity of the in-planemagnetic recording medium 2 was in the range between 150 kA/m and 300kA/m. According to the results of this experiment, it is suitable todetermine the correction amount α to be in the range between 0.05 μm and1.0 μm based on the values of the lengths a, b of the magnetictransition areas, and also to determine the values of α/a and α/b to bein the range between 0.01 and 0.8.

[0087] With this correction amount α, the quantity of pulse shift in thereproduction waveform by the magnetic head could be suppressed to notmore than the permissible limit of the detection window width of thereproduction signal processing circuit.

[0088] The pattern of the ferromagnetic thin films 3 on the surface ofthe master information carrier 1 can be manufactured, like theconventional pattern of the ferromagnetic thin films shown in FIG. 22,by using a variety of known lithographic techniques. Now, FIG. 1 shows aconfiguration example in which the cross-sectional shape of theferromagnetic thin films 3 is substantially rectangular, but it is notnecessarily required to form the rectangular cross-sectional shape asshown in FIG. 1 depending on the characteristics of the appliedlithographic technique.

[0089]FIG. 2 and FIG. 3 show other configurations of the masterinformation carrier of the present invention provided with theferromagnetic thin films 3 having the cross-sectional shape thatgenerally is a substantially truncated or frusto shape. With respect tothis kind of master information carrier 1, the pattern length A of theoutermost surface portion facing the in-plane magnetic recording medium2 in the ferromagnetic thin films 3 and the length between the patternsB should be controlled.

[0090] In other words, as shown in FIG. 2 and FIG. 3, the same effect asthat in the configuration shown in FIG. 1 can be obtained by determiningthe pattern length A of the outermost surface portion facing thein-plane magnetic recording medium 2 in the ferromagnetic thin films 3having a cross-sectional truncated shape (the length of the masterinformation carrier 1 in the circumferential direction) to be largeronly by the appropriate correction amount α than the desired lengthbetween the magnetic transition areas a, and on the contrary bydetermining the distance B between the patterns of the ferromagneticthin films 3 to be smaller only by the correction amount α than thedesired length between the magnetic transition areas b.

[0091] Furthermore, FIG. 1 shows a configuration example of the masterinformation carrier 1 in which the surface of the ferromagnetic thinfilm 3 and the surface of the nonmagnetic base 8 are not stepped but aresubstantially flat. However, the configuration of the master informationcarrier according to the present invention is not limited hereto. Forexample, as shown in FIG. 2, the surface of the ferromagnetic thin film3 may be recessed by a substantially constant amount relative to thesurface of the nonmagnetic base 8. On the contrary, as shown in FIG. 3,the surface of the ferromagnetic thin film 3 may protrude by asubstantially constant amount from the surface of the nonmagnetic base8. Moreover, although a specific illustration is omitted here, it mayalso be configured such that the ferromagnetic thin films 3 are formedas protrusions on the surface of the nonmagnetic base 8 (See FIG. 24).

[0092] However, in the configuration of FIG. 2, if the recessed amountof the surface of the ferromagnetic thin film 3 relative to thenonmagnetic base 8 is too large, there is fear of causing a spacing losswhen signals are recorded. This spacing loss changes according to therecording density of signals, but it is generally preferable todetermine the above-mentioned recessed amount to be not more than 100nmwhen a preformat recording of signals with the lengths between themagnetic transition areas a or b of not more than several μm isperformed.

[0093] Furthermore, in the configuration of FIG. 3, when the protrudingamount of the surface of the ferromagnetic thin film 3 relative to thenonmagnetic base 8 is too large, there is fear of not obtainingsufficient durability for the master information carrier. In viewthereof, it is preferable to determine the above-mentioned protrudingamount in the configuration of FIG. 3 to be not more than 100 nm.

[0094] In addition, in the master information carrier 1 shown in FIG. 1to FIG. 3, it is not necessarily required to strictly control thecorrection amount α in order to exactly realize the desired lengthsbetween the magnetic transition areas a and b on the in-plane magneticrecording medium 2. In other words, with the correction amount a, thequantity of pulse shift in the reproduction waveform by the magnetichead should be suppressed to not more than the permissible limit of thedetection window width of the reproduction signal processing circuit. Inview thereof, it is sufficient to determine the correction amount α soas to control the desired lengths between the magnetic transition areasa and b to be in the range including a certain tolerance in addition tothe optimum values to be realized accurately.

[0095] Here, in comparing the configurations of FIG. 1 to FIG. 3 witheach other, in order to realize the desired lengths between the magnetictransition areas a and b exactly, in the strict sense of the word, it isnecessary to increase the correction amount α in the configuration ofFIG. 2 versus the configuration of FIG. 1 and to reduce the correctionamount α in the configuration of FIG. 3 versus the configuration ofFIG. 1. In most cases, however, the difference in the correction amountα between the configurations of FIG. 1 to FIG. 3 is so small as not tobe more than the permissible limit of the detection window width of thereproduction signal processing circuit, so that this difference may beignored.

[0096] An example of the embodiment according to the present inventionwas described above, but the present invention can be applied to variousembodiments other than this example. For example, the above-mentionedexplanation referred to an example of applying the present invention toa magnetic recording medium to be mounted on a hard disc drive or thelike. However, the present invention is not limited hereto and isapplicable to magnetic recording media such as a flexible magnetic disc,a magnetic card and a magnetic tape, thereby obtaining the same effectas described above.

[0097] Furthermore, with regard to the information signals to berecorded in the magnetic recording medium, preformat signals such as aservo signal for tracking, an address information signal and areproduction clock signal were used as examples, but the informationsignals applicable to the present invention also are not limited to theabove-mentioned signals.

[0098] For example, by using the configuration of the present invention,it is in principle also possible to record various data signals or audioand video signals. In this case, by employing the magnetic recordingmethod for a magnetic recording medium using the master informationcarrier of the present invention, the software recording medium can bemass-produced by duplication and provided inexpensively.

SECOND EMBODIMENT

[0099] In the following, a second embodiment of the present inventionwill be explained.

[0100] First, the preformat recording step using a master informationcarrier, which is performed as one of the steps for manufacturing avertical magnetic recording medium, will be explained briefly byreferring to FIG. 7A to FIG. 7C. FIG. 7A to FIG. 7C are cross-sectionalviews taken in the circumferential direction of a disc of a verticalmagnetic recording medium 21, and the lateral direction of the surfacealso matches the time base direction at the time when a magnetizedpattern to be recorded in the vertical magnetic recording medium 21 isreproduced with a magnetic head.

[0101] First, as shown in FIG. 7A, the vertical magnetic recordingmedium 21 in which preformat signals are to be recorded is prepared.Next, as shown in FIG. 7B, the surface of a master information carrier22 according to the configuration shown in FIG. 8 or FIG. 9 is contactedclosely with the surface of the vertical magnetic recording medium 21,and an applied magnetic field 25 is applied in the direction parallel tothe film surface of ferromagnetic thin films 32 on the masterinformation carrier 22.

[0102] The direction of this applied magnetic field 25 also matches thedirection parallel to the film surface of a magnetic layer in thevertical magnetic recording medium 21. In addition, FIG. 7B shows anexample of using the master information carrier 22 in which theferromagnetic thin films 23 are buried in the surface of a nonmagneticbase 24 as shown in FIG. 8, but the master information carrier 22 onwhich the ferromagnetic thin films 23 are protruding from the surface ofthe nonmagnetic base 24 as shown in FIG. 9 may be used as well.

[0103] As shown in FIG. 7B, by applying the magnetic field 25, leakageflux 26 corresponding to a shape pattern of the ferromagnetic thin films23 is generated on the surface of the master information carrier 22.This leakage flux 26 substantially contains a large quantity ofdirectional components parallel to the film surface of the ferromagneticthin film 23, but in the vicinity of the both edges of the ferromagneticthin film 23, the leakage flux 26 has a relatively large quantity ofvertical directional components. Due to this magnetic field with thevertical directional components, recorded magnetization 27 with apattern corresponding to the shape pattern of the ferromagnetic thinfilms 23 is recorded in the vertical magnetic recording medium 21 asshown in FIG. 7C.

[0104] Here, a vertical magnetic field distribution contributing to therecording in the present embodiment and a reproduction waveform of therecorded magnetization are shown in FIG. 10. As it is clear by comparingFIG. 10 with FIG. 27, which shows the vertical magnetic fielddistribution contributing to the recording in the conventional methoddisclosed in JP10(1998)-40544A and the reproduction waveform of therecorded magnetization, the magnetic field 65 is applied perpendicularto the ferromagnetic thin films 63 in the conventional method, while themagnetic field 25 is applied in the direction parallel to the filmsurface of the ferromagnetic thin films 23 in the present embodiment.Accordingly, in the present embodiment, the demagnetizing field insideeach pattern of the ferromagnetic thin films 23 is small, and magneticpaths with small magnetic resistance are formed successively in thein-plane of the master information carrier 22. As a result, in thepresent embodiment, as shown in FIG. 10, an extremely large volume ofleakage flux 26 can be obtained compared to the leakage flux 66 obtainedby the conventional method shown in FIG. 27.

[0105] As already described, this leakage flux 26 substantially containsa large quantity of directional components parallel to the film surfaceof the ferromagnetic thin films 23, but a sufficiently large volume ofvertical directional components can be obtained in the vicinity of theboth edges of the ferromagnetic thin film 23 compared to the volume 31of the applied magnetic field 25 (the volume of this applied magneticfield shown in FIG. 10 is the volume of directional components parallelto the film surface of the ferromagnetic thin films 23). Therefore, therecorded magnetization in the vertical magnetic recording medium 21 alsois large in correspondence with the value of the residual magnetizationintrinsic in the vertical magnetic recording medium 21, and also withregard to a reproduction waveform 32 reproduced by this recordedmagnetized pattern, an amplitude almost as large as a reproductionsignal amplitude 33 reproduced from the magnetized pattern recorded bythe conventional magnetic head can be obtained.

[0106] It should be noted here that the vertical magnetic fielddistribution in the magnetic recording method of the present embodimentdiffers from that in the conventional method shown in FIG. 27 in thatthis vertical magnetic field distribution shows a large magnetic fieldamplitude with reversed polarities to each other in the vicinity of theboth edges of the ferromagnetic thin film 23. In other words, with theconventional method shown in FIG. 27, the vertical magnetic fielddistribution corresponding to the pattern shape of the ferromagneticthin films can be obtained, but this merely was an overall amplitudechange in the same polarity. Therefore, in order to record a recordedmagnetized pattern in which magnetization areas with reversed polaritiesto each other are arranged alternately via a magnetic transition area,and thus to obtain a larger reproduction signal amplitude, it wasnecessary to provide initial magnetization by erasing magnetizationthrough application of a d.c. magnetic field in one direction.

[0107] On the other hand, according to the magnetic recording method ofthe present embodiment, by applying the magnetic field 25, it ispossible to obtain a vertical magnetic field distribution that has amagnetic field amplitude with reversed polarities to each other in thevicinity of both edges of each pattern of the ferromagnetic thin films23 and also with a large volume. Therefore, without performing theinitialization with application of a d.c. magnetic field, a recordedmagnetized pattern can be formed in which magnetization areas withreversed polarities to each other are arranged alternately via amagnetic transition area, and thus a larger reproduction signalamplitude can be obtained. In other words, the magnetic recording methodof the present embodiment does not necessarily require erasing themagnetization by applying a d.c. magnetic field in one direction, sothat the problem in the conventional method does not occur in that it isdifficult to obtain the state of substantially stable and uniformmagnetization by erasing the magnetization by applying a d.c. magneticfield in one direction in a vertical magnetic recording medium.

[0108] In addition, also in the magnetic recording method of the presentembodiment, it is possible to erase the magnetization of the verticalmagnetic recording medium 21 in advance by applying a d.c. magneticfield in one direction and to provide initial magnetization as shown inFIG. 11A. Furthermore, also by applying a magnetic field alternately inopposite directions or through application of a thermomagnetizationmethod or the like, the magnetization of the vertical magnetic recordingmedium 21 can be erased to a neutral point in advance. For example, whena preformat recording is performed for the second time by using themagnetic recording method of the present embodiment for a verticalmagnetic recording medium in which certain magnetization signals arealready recorded, for the purpose of preventing unnecessarymagnetization signals from remaining, it is effective to erasemagnetization in advance by applying a magnetic field in one directionor alternately in opposite directions or through application of athermomagnetization method. In any case, the recorded magnetized patternthat can be obtained in consequence does not differ much from thatrecorded by the process shown in FIG. 7A to FIG. 7C, and reproductionsignals of excellent quality can be obtained.

[0109] Furthermore, the reproduction waveform reproduced from themagnetized pattern recorded by the magnetic recording method of thepresent embodiment does not have a rectangular shape peculiar tovertical magnetic recording such as the reproduction waveform reproducedfrom the magnetized pattern recorded by the conventional method shown inFIG. 27 or the reproduction waveform reproduced from the magnetizedpattern recorded by a magnetic head, but instead has the samesingle-peak-shape as the reproduction waveform of longitudinal magneticrecording (in-plane magnetic recording). For detecting the rectangularwaveform peculiar to the vertical magnetic recording with a signalprocessing circuit used for a recording reproduction device of thepresent in-plane magnetic recording medium, this rectangular shape needsto be differentiated and converted to the same single-peak waveform asthat of longitudinal magnetic recording.

[0110] However, the waveform obtained from the magnetized patternrecorded by the magnetic recording method of the present embodiment isthe same single-peak waveform as that of longitudinal magnetic recordingfrom the beginning, so that such a differentiation process isunnecessary. Therefore, a magnetic recording reproduction device to bemounted with a magnetic disc in which the preformat recording isperformed by the magnetic recording method of the present embodimentalso can be advantageous in view of the cost, due to the fact that anextra differentiation processing circuit is no longer needed in thedetection system of servo signals.

[0111] In order to perform a recording in a vertical magnetic recordingmedium having larger coercivity by the magnetic recording method of thepresent embodiment, a larger vertical magnetic field is needed. In thiscase, the ferromagnetic thin films constructing the shape patternscorresponding to the preformat signals in the master information carrierare required to have a large saturation magnetic flux density. Accordingto the examinations conducted by the present inventors, it is preferablethat the ferromagnetic thin films have a saturation magnetic fluxdensity of at least 0.8 T, and not less than 1.0 T is more preferable.

[0112] Furthermore, the ferromagnetic thin films 23 are required to bemagnetized quickly by the applied magnetic field 25 and also to exhibitthe effect of shielding the magnetic flux in the vicinity thereof. Inview of the foregoing, it is preferable that the ferromagnetic thinfilms 23 have a relatively high magnetic permeability, and particularlya relative permeability of not less than 100 is preferable.

[0113] Furthermore, for achieving excellent recording performance by themagnetic recording method of the present embodiment, it is necessarythat the demagnetizing field in the in-plane direction of the filminside each pattern of the ferromagnetic thin films 23 is small, andthat magnetic paths with small magnetic resistance are formedsuccessively in the in-plane of the master information carrier 22.Therefore, contrary to the conventional method shown in FIG. 27, it isnot preferable to increase the thickness of the ferromagnetic thin filmsin ratio to the pattern length thereof.

[0114] According to the examinations conducted by the present inventors,it is preferable that the thickness of the ferromagnetic thin films 23is about as large as or not larger than the pattern length of theferromagnetic thin films 23 in the circumferential direction of themaster information carrier 22. The pattern length of this ferromagneticthin film 23 is formed so as to substantially match the length ofmagnetization reversal in the magnetized pattern to be recorded (thatis, the distance between two magnetic transition areas adjacent to eachother). Therefore, the minimum value of the pattern length of theferromagnetic thin films existing on one master information carrier 22substantially matches a bit length in the case of a digital signal andhalf of the shortest recording wavelength in the case of an analogsignal. Thus, the thickness of the ferromagnetic thin films 23 may bedetermined to be not more than the bit length of the digital informationsignal to be recorded in the vertical magnetic recording medium 21 ornot more than half of the shortest recording wavelength of the analoginformation signal to be recorded in the vertical magnetic recordingmedium 21.

[0115] Next, the magnetic recording method of the present embodimentwill be explained more in detail.

[0116]FIG. 12 is a cross-sectional view showing one example of aschematic configuration of a magnetic recording device used for themagnetic recording method of the present embodiment. In this magneticrecording device, first, the master information carrier 22 is positionedon the surface of the vertical magnetic recording medium 21 arranged ona flange 38. Next, air present between the vertical magnetic recordingmedium 21 and the master information carrier 22 is exhausted from acentral hole 41 of the vertical magnetic recording medium by an exhaustdevice 40 connected to the flange 38 via an exhaust duct 39. Thus, dueto the decompression state achieved between the vertical magneticrecording medium 21 and the master information carrier 22, both of themare contacted closely. In addition, 37 shown in FIG. 12 is a magnetictranscription head for providing the master information carrier 22 withthe applied magnetic field 25.

[0117] The magnetic transcription head 37, which is arranged near theback face of the master information carrier 22, is configured so as toperform a relative movement against the master information carrier 22while maintaining a constant distance from the back face of the masterinformation carrier 22. Due to this configuration, the applied magneticfield required for the transcription recording can be provided overnecessary areas of the master information carrier 22.

[0118] An enlarged view of a configuration example near the magnetictranscription head 37 in the magnetic recording device shown in FIG. 12is shown in FIG. 13. FIG. 13 shows the configuration example in which amagnetic transcription head 37 a is made of a permanent-magnet block.The magnetic transcription head 37a made of a permanent-magnet block ismagnetized in the direction parallel to the side facing the masterinformation carrier 22 as shown by arrow 42 so as to provide theferromagnetic thin films 23 of the master information carrier 22 withthe applied magnetic field 25 in the in-plane direction of the film. Inthe configuration of FIG. 13, by rotating the magnetic transcriptionhead 37a around the disc center of the vertical magnetic recordingmedium 21, the applied magnetic field needed for the transcriptionrecording can be provided over all the wedge pattern areas 34. Here, thewedge pattern area 34 is an area where the pattern of the ferromagneticthin films 23 is formed.

[0119] An enlarged view of another configuration example near themagnetic transcription head 37 in the magnetic recording device shown inFIG. 12 is shown in FIG. 14. FIG. 14 shows the configuration example inwhich a magnetic transcription head 37 b is formed as a ring type with afirst magnetic core 43 and a second magnetic core 44 made of aferromagnetic material, and also in which the first magnetic core 43 isan electromagnet equipped with a coil winding 45. The magnetictranscription head 37 b has a gap between the first magnetic core 43 andthe second magnetic core 44 so as to provide the surface facing themaster information carrier 22 with the applied magnetic field 25 in thefilm in-plane direction of the ferromagnetic thin films 23 on the masterinformation carrier 22. Also in the configuration of FIG. 14, byrotating the magnetic transcription head 37 b around the disc center ofthe vertical magnetic recording medium 21, the applied magnetic fieldneeded for the transcription recording can be provided over all thewedge pattern areas 34.

[0120] In the following, the operating conditions and so forth of themagnetic transcription head in the magnetic recording device at the timewhen the magnetic recording method of the present embodiment isperformed will be explained by referring to some specific embodiments.

[0121] First, the operation of a magnetic transcription head in amagnetic recording device provided with the magnetic transcription head37 a of a permanent magnet block type as shown in FIG. 13 will beexplained. FIG. 15B and FIG. 15C, FIG. 16B and FIG. 16C, and FIG. 17Band FIG. 17C show the relative position relationship between thevertical magnetic recording medium, the master information carrier andthe magnetic transcription head at the time when a preformat recordingis performed for the vertical magnetic recording medium using themagnetic recording device and are cross-sectional views taken on brokenline MM′ indicated on the surface of the master information carriers 22shown in FIG. 15A, FIG. 16A and FIG. 17A.

[0122] When the preformat recording is performed, as shown in FIG. 17B,the magnetic transcription head 37 a is shifted relative to the masterinformation carrier 22 toward the direction shown by an arrow 46 whilemaintaining a constant distance from the back face of the masterinformation carrier 22. At the time when the applied magnetic fieldneeded for the transcription recording is provided over all the wedgepattern areas 34 of the master information carrier 22, the preformatrecording is completed, and the magnetic transcription head 37 a ismoved relatively far away from the master information carrier.

[0123]FIG. 17C shows the state of separating the master informationcarrier 22 far away by shifting the magnetic transcription head 37 a inthe direction perpendicular to the surface of the master informationcarrier 22 (in the direction shown by an arrow 47 in FIG. 17C). At thistime, it is not preferable to perform the operation of separating themagnetic transcription head 37 a in a position in which the magnetictranscription head 37 a faces the wedge pattern 34 of the masterinformation carrier 22. This is because, depending on the distributionof the leakage magnetic flux 26 from the magnetic transcription head 37a, the ferromagnetic thin films 23 inside the wedge pattern area 34 maybe magnetized in the direction perpendicular to the film surface, and asa result, the recorded magnetized pattern in the vertical magneticrecording medium 21 may be erased or demagnetized.

[0124] To prevent the above-described phenomenon from occurring and tocomplete the preformat recording appropriately, it is preferable toperform the operation of separating the magnetic transcription head 37 afrom the master information carrier 22 in a position in which themagnetic transcription head 37 a faces an area between wedges 35 wherethe pattern of the ferromagnetic thin films 23 is not formed. Such apreferable embodiment is shown in FIG. 15C. In FIG. 15C, the separatingoperation is performed in the position where the magnetic transcriptionhead 37 a faces the area between wedges 35 where the pattern of theferromagnetic thin films 23 is not formed by shifting the magnetictranscription head 37 a in the direction perpendicular to the surface ofthe master information carrier 22 (in the direction shown by the arrow47), so that the recorded magnetized pattern is neither erased nordemagnetized as described above.

[0125] Depending on the configuration of a magnetic transcriptiondevice, particularly on the arrangement of machine parts included inthis device, it is sometimes difficult to perform the separatingoperation by shifting the magnetic transcription head 37 a in thedirection perpendicular to the surface of the master information carrier22. In such a case, as long as the operation of separating the magnetictranscription head 37 a is performed in the position in which themagnetic transcription head 37 a faces the area between wedges 35 wherethe pattern of the ferromagnetic thin films 23 is not formed, it is alsopossible to perform the separating operation by shifting the magnetictranscription head 37 a in the direction parallel to the surface of themaster information carrier 22 as illustrated in FIG. 16C (in thedirection 47 shown in FIG. 16C).

[0126] In the master information carrier 22 shown in FIG. 16B and FIG.16C, the areas between wedges 35, where the shape pattern of theferromagnetic thin films is not formed, are formed in a concave shapeadjacent the wedge pattern areas 34. This works as an air channel forevacuating the air between the master information carrier and themagnetic recording medium. As already explained by referring to FIG. 12,in the magnetic recording device used for performing the magneticrecording method of the present embodiment, air present between thevertical magnetic recording medium 21 and the master information carrier22 is exhausted from the central hole 41 of the vertical recordingmedium 21 by the exhaust device 40, and due to the decompression stateachieved between them, both of them are contacted closely. By formingthe area between wedges 35 into a concave shape adjacent the wedgepattern area 34 as shown in FIG. 16B etc., exhaust paths of air betweenthe vertical magnetic recording medium 21 and the master informationcarrier 22 are secured sufficiently. As a result, the decompressionstate between the vertical magnetic recording medium 21 and the masterinformation carrier 22 can be achieved more completely and easily.

[0127] In addition, whether to perform the operation of separating themagnetic transcription head 37 a from the master information carrier 22in the direction perpendicular to the surface of the master informationcarrier 22 as shown in FIG. 15C or in the parallel direction thereto asshown in FIG. 16C, is not dependent on whether the area between wedges35 is formed in a concave shape or not. According to the configurationof the magnetic recording device, either combination can be selected.

[0128] Next, the operation of the magnetic transcription head 37 b atthe time when a preformat recording is performed for the verticalmagnetic recording medium 21 by using the magnetic recording deviceprovided with the ring type magnetic transcription head 37 b shown inFIG. 14 will be explained by referring to FIG. 18A to FIG. 18C. FIG. 18Band FIG. 18C are cross-sectional views taken on broken line MM′indicated on the surface of the master information carriers 22 shown inFIG. 18A.

[0129] When the preformat recording is performed, as shown in FIG. 18B,the magnetic transcription head 37 b is shifted relative to the masterinformation carrier 22 toward the direction shown by the arrow 46 whilemaintaining a constant distance from the back face of the masterinformation carrier 22. In this process, the coil winding 45 is providedwith coil current in the magnetic transcription head 37 b so as to givean appropriate applied magnetic field to the master information carrier22. At the time when the applied magnetic field needed for thetranscription recording is provided over all the wedge pattern areas 34,the preformat recording is completed, and the, magnetic transcriptionhead 37 b is moved relatively far away from the master informationcarrier 22.

[0130] In the case of this magnetic transcription head 37 b, the coilcurrent can be switched off to stop providing the master informationcarrier 22 with the applied magnetic field. Therefore, if the coilcurrent is switched off prior to the operation of separating themagnetic transcription head 37 b from the master information carrier 22,as shown in FIG. 18C, even if the separating operation is performed in aposition in which the magnetic transcription head 37 b faces the wedgepattern area 34 on the master information carrier 22, there is no fearthat the magnetized pattern recorded on the vertical magnetic recordingmedium 21 will be erased or demagnetized, and excellent results can beobtained.

[0131]FIG. 18C shows the state of separating the magnetic transcriptionhead 37 b in the direction perpendicular to the surface of the masterinformation carrier 22, but excellent results can be obtained also inthe case of separating it in the direction parallel to the surface.

[0132] Next, yet another example of performing the magnetic recordingmethod according to the present embodiment will be shown by referring toFIG. 19A to FIG. 19C. FIG. 19B and FIG. 19C are cross-sectional viewstaken on broken line MM′ indicated on the surface of the masterinformation carrier 22 shown in FIG. 19A.

[0133] A magnetic transcription head 37 c shown in FIG. 19B is also aring type as the magnetic transcription head 37 b shown in FIG. 18Betc., but while the magnetic transcription head 37 b is equipped withthe coil winding 45, the configuration of this magnetic transcriptionhead 37 c differs in that the first magnetic core 43 and the secondmagnetic core 44 are opposed to each other via a permanent-magnet block49. In other words, when this magnetic transcription head 37 c is used,the leakage flux 26 for providing the master information carrier 22 withthe applied magnetic field is not generated through excitation of themagnetic core by the coil current, but as shown by the arrow 42 in FIG.19B, the leakage flux 26 is generated by the residual magnetization ofthe permanent-magnet block 49 magnetized in the magnetic path directionof the ring type magnetic core.

[0134] Thus, it is not possible to stop providing the master informationcarrier 22 with the applied magnetic field by switching off the coilcurrent prior to the operation of separating the magnetic transcriptionhead from the surface of the master information carrier as shown in FIG.18C. Therefore, as in FIG. 15C and FIG. 16C, it is necessary to performthe operation of separating the magnetic transcription head 37 c fromthe master information carrier 22 in a position in which the magnetictranscription head 37 c faces the area between wedges 35 where thepattern of the ferromagnetic thin films 23 is not formed.

[0135] However, compared to the magnetic transcription head 37 a of apermanent magnet block type shown in FIG. 13 etc., the magnetictranscription head 37 c of a ring type shown in FIG. 19B etc. has alarger volume due to its configuration. Therefore, even if the magnetictranscription head 37 c is in the position of facing the area betweenwedges 35 where the pattern of the ferromagnetic thin films 23 is notformed, it is sometimes difficult to achieve the state in which themagnetization is not completely applied to the neighboring wedge patterareas 34.

[0136] In such a case, as shown in FIG. 19A, it is also possible to usea master information carrier in which one piece or about two piecesamong the plurality of wedge pattern areas 34 provided at a constantangle interval in one circle, that is, within an angle of 360 degrees ofthe master information carrier 22, is missing. Due to thisconfiguration, at least in one portion within the circle of the disc, anarea between wedges 35′ having a sufficiently large area relative to thesize of the magnetic transcription head 37 c can be provided.

[0137] In other words, when the operation of separating the magnetictranscription head 37 c from the master information carrier 22 isperformed in the position in which the magnetic transcription head 37 cfaces this area between wedges 35′ having a large area, it is possibleto obtain excellent results without subjecting the neighboring wedgepattern areas 34 to the applied magnetic field.

[0138] In addition, the number of the wedge pattern area 34 on themaster information carrier 22 generally is determined with aconsiderable degree of redundancy against the positioning precision ofthe magnetic head required for the magnetic recording reproductiondevice, and even in the case where one piece or about two pieces aremissing in one circle of the disc, the required servo trackingperformance often can be realized without any problem. Furthermore,after the vertical magnetic recording medium 21 in which the preformatrecording was performed by using the master information carrier 22 shownin FIG. 19A is mounted on a magnetic recording reproduction device, themagnetized pattern corresponding to the missing wedge pattern areas canbe recorded additionally with reference to other magnetized patterns inthe magnetic recording medium 21 by using the magnetic head of themagnetic recording reproduction device.

[0139]FIG. 19C showed the state in which the operation of separating themagnetic transcription head 37 c was performed by shifting the magnetictranscription head 37 c in the direction perpendicular to the surface ofthe master information carrier 22 (in the direction shown by the arrow47). However, as long as the magnetic transcription head 37 c is in theposition facing the area between wedges 35/35′, as shown in FIG. 20C,the separating operation can be performed by shifting the magnetictranscription head 37 c in the direction parallel to the surface of themaster information carrier 22 (in the direction 47 shown in FIG. 20C).

[0140] Furthermore, FIG. 19B and FIG. 19C showed examples of using themaster information carrier 22 in which the area between wedges 35 wasformed into a concave shape adjacent the wedge pattern area 34 in orderto secure exhaust paths at the time when air between the verticalmagnetic recording medium 21 and the master information carrier 22 isexhausted, while FIG. 20B and FIG. 20C showed examples of using themaster information carrier 22 in which the area between wedges 35 andthe wedge pattern area 34 are formed flush. However, whether to performthe separating operation of the magnetic transcription head 37 c in thedirection perpendicular to the surface of the master information carrier22 or in the parallel direction thereto is not dependent on whether thearea between wedges 35 is formed in a concave shape or not. According tothe configuration of the magnetic recording device, either combinationcan be selected.

[0141] The second embodiment of the present invention was describedabove, but the present invention is not limited to the presentembodiment and can be applied to a variety of embodiments. For example,the present embodiment referred to an example of applying it to avertical magnetic recording medium to be mounted mainly on a hard discdrive or the like. However, the present invention is not limited heretoand is applicable to other vertical magnetic recording media such as aflexible magnetic disc, a magnetic card and a magnetic tape, therebyobtaining the same effect as described above.

[0142] Furthermore, with regard to the information signals to berecorded in the vertical magnetic recording medium, preformat signalssuch as a servo signal for tracking, an address information signal and areproduction clock signal were used as examples, but the informationsignals applicable to the present invention also are not limited to theabove-mentioned signals. For example, by using the present invention, itis in principle also possible to record various data signals or audioand video signals. In this case, by employing the magnetic recordingmethod for a vertical magnetic recording medium using the masterinformation carrier of the present invention, the software recordingmedium can be mass-produced by duplication and provided inexpensively.

[0143] Industrial Applicability

[0144] As described above, with the master information carrier used forperforming a static surface recording of information signals in anin-plane magnetic recording medium, it is now possible to record adesired magnetized pattern closer to a set point by modifying the arrayof patterns in the ferromagnetic thin films. Accordingly, a magneticrecording medium arising no reproduction signal errors can be provided.As a result, in the preformat technology of performing a static surfacerecording, higher performance related to the quality of signals to berecorded in the magnetic recording medium can be further promoted.

[0145] Furthermore, when the master information carrier is used toperform a static surface recording of information signals in a verticalmagnetic recording medium, more excellent recording performance can beachieved, and thus a magnetic recording medium exhibiting reproductionsignals of higher quality can be provided.

1-13. (Cancelled)
 14. A method for producing a vertical magneticrecording medium, the method comprising the step of: bringing a surfaceof a master information carrier in close contact with a surface of thevertical magnetic recording medium, the surface of the masterinformation carrier having an information signal according to afiguration pattern of an array of ferromagnetic thin films that aredeposited on a surface of a substrate, and applying a magnetic fieldthereto, so as to record the information signal corresponding to thearray of the ferromagnetic thin films as magnetization information inthe vertical magnetic recording medium, wherein the magnetic field isapplied in a direction parallel to surfaces of the ferromagnetic thinfilms and a surface of a magnetic layer of the vertical magneticrecording medium.
 15. The method according to claim 14, furthercomprising the step of: erasing magnetization of the vertical magneticrecording medium to a neutral point at least either by applying amagnetic field alternately in opposite directions or through applicationof a thermomagnetization method, prior to the step of bringing thesurface of the master information carrier in close contact with thesurface of the vertical magnetic recording medium.
 16. The methodaccording to claim 14, further comprising the step of: magnetizing thevertical magnetic recording medium uniformly in a direction vertical tothe surface of the magnetic layer of the vertical magnetic recordingmedium by applying a d.c.
 17. The method according to claim 14, whereinthe ferromagnetic thin films have either a thickness of not more than abit length of a digital information signal to be recorded in thevertical magnetic recording medium or a thickness of not more than halfof a shortest recording wavelength of an analog information signal to berecorded in the vertical magnetic recording medium.
 18. The methodaccording to claim 14, wherein the magnetic field is provided using amagnetic transcription head arranged in a vicinity of a back face of themaster information carrier, the method further comprising the steps of:shifting the magnetic transcription head relative to the masterinformation carrier while maintaining a constant distance between themagnetic transcription head and the back face of the master informationcarrier in a state in which the surface of the master informationcarrier and the surface of the vertical magnetic recording medium are inclose contact with each other, so that the magnetic field is appliedover a region that requires the magnetic field, and separating themagnetic transcription head at a predetermined position farther from themaster information carrier, after the step of shifting the magnetictranscription head.
 19. The method according to claim 18, wherein themagnetic transcription head is an electromagnet formed by providing amagnetic core made of a ferromagnetic material with a coil winding, forthe step of shifting the magnetic transcription head relative to themaster information carrier while maintaining a constant distance betweenthe magnetic transcription head and the back face of the masterinformation carrier, a coil current is supplied to the magnetictranscription head, and prior to the step of separating the magnetictranscription head farther from the master information carrier, thesupply of the coil current is stopped.
 20. The method according to claim18, wherein the master information carrier has, on its surface, an areawhere a figuration pattern of ferromagnetic thin films corresponding toan information signal is formed, and an area where a figuration patternof ferromagnetic thin films is not formed, and the step of separatingthe magnetic transcription head farther from the master informationcarrier is carried out by moving the magnetic transcription head in adirection vertical to the surface of the master information carrier, ata position where the magnetic transcription head is opposed to the areawhere a figuration pattern of the ferromagnetic thin films is notformed.
 21. The method according to claim 18, wherein the masterinformation carrier has, on its surface, an area where a figurationpattern of ferromagnetic thin films corresponding to an informationsignal is formed, and an area where a figuration pattern offerromagnetic thin films is not formed, and the step of separating themagnetic transcription head farther from the master information carrieris carried out by moving the magnetic transcription head in a directionparallel to the surface of the master information carrier, at a positionwhere the magnetic transcription head is opposed to the area where afiguration pattern of the ferromagnetic thin films is not formed.
 22. Amethod for producing a vertical magnetic recording medium, the methodcomprising the step of: bringing a surface of a master informationcarrier in close contact with a surface of the vertical magneticrecording medium, the surface of the master information carrier havingan information signal according to a figuration pattern of an array offerromagnetic thin films that are deposited on a surface of a substrate,and applying a magnetic field thereto, so as to record the informationsignal corresponding to the array of the ferromagnetic thin films asmagnetization information in the vertical magnetic recording medium,wherein the ferromagnetic thin films are magnetized in a directionparallel to the surfaces thereof, by applying the magnetic field in thedirection parallel to the surfaces of the ferromagnetic thin films and asurface of a magnetic layer of the vertical magnetic recording medium,and the magnetic layer of the vertical magnetic recording medium ismagnetized in a direction vertical to the surface thereof, with use of avertical directional component of a leakage magnetic flux that leaks outbetween adjacent ferromagnetic thin films.